The conventional vacuum-operated time lag switch – used with stair and corridor lighting to save electricity – will operate for up to five minutes, but can be dangerous to stair users because it gives no warning before cutting out. The control, which can also be fitted in place of any square-plate switch, comes in a touch pad version.
However the most up-to-date version is a device which incorporates a time lag control with the touch pad facility but maintains a degree of light ; the light does not cut out, but fades and then holds indefinitely at a safety level. A slight touch will then turn off the light electronically. This is also a standard square-plate switch and can replace any one-way switch without wiring modifications.
Also available is a master time lag dimmer of the touch pad type which can be used in a two-way or intermediate switching circuit. It is fitted in place of one of the two-way switches (or intermediate switches in a multi-switching circuit) and the other remains as an ordinary switch; but it also operates the light or lights and begins the time lag sequence.
Burglar deterrent switches
Leaving lights on in a house may deter a casual would-be intruder, but it is unlikely to fool a professional house-breaker. Deterrent lighting should be switched on and off at the proper time and solar-operated devices, which go on at sundown and off at sunrise, are available.
One of the most useful for the home is a dimmer switch fitted with a photo cell which enables the light to be left on at a low level and therefore is not expensive to run. This can be used to replace any modern square-plate one-way or two-way switch without modification to the wiring.
Another type of burglar deterrent is the combined on-off time switch which operates as an ordinary switch and can be set to turn lights on or off automatically at frequent intervals to give the impression the house is being used. Bear in mind, house-breakers know which rooms are used when.